Some fire alarm systems have sounders built into the bases which receive the detectors. These are referred to in the industry as “behind detector” sounders. Such sounders are as a consequence usually on the ceiling of the protected area. The specifications of other fire alarm systems require the use of wall mounted sounders. Such sounders are “stand alone” units and do not incorporate detectors.
Most sounders are powered directly off the communication lines and hence the power available is small. As a consequence such sounders must be efficient, and the present invention seeks to provide a sounder which produces acceptable all round sound levels using the power available on the communication lines.